1. Field of the Invention
The present invention relates to an adaptive frequency selective baseband communications method using orthogonal codes and, more particularly, to an adaptive frequency selective baseband communications method using orthogonal codes capable of increasing detection accuracy in detecting a reception signal by adaptively selecting a frequency band of a transmission signal to avoid noise varied by surrounding environments and minimizing interference between transmission signals by using codes with orthogonality in human-body communications using a human body as a medium. In addition, the present invention relates to a method of obtaining a time diversity or frequency diversity gain under conditions in which human body users interfere with each other or in which heavy interference induced from an electronic device is generated, to thereby implement a low-power, stable human-body communications method.
2. Description of the Related Art
In general, human-body communications refers to a technique that transfers signals between devices connected with a human body having conductivity by using the human body as a communications channel. With the human-body communications technique, a network for communications between various mobile devices such as a personal digital assistant (PDA), a mobile personal computer, a digital camera, an MP3 player, a mobile phone, and the like, or communications with a fixed device such as a printer, a TV, an entrance system, or the like, is established as a user simply comes in contact therewith.
In more detail, the human-body communications is a technique that transmits information by using a limited frequency band in which the strength of a signal transmitted via a human body serving as a waveguide is stronger than that of a signal radiated to the outside of the human body, having the properties of consuming small energy and being resistant to external noise.
Meanwhile, frequency selective baseband communications refers to a transmission technique only allowing the use of codes having the best frequency characteristics for a user-desired frequency band, thus simplifying an analog transmission/reception unit. Namely, the frequency selective baseband communications allows for the selection of a desired frequency band while performing baseband transmission.
With human-body communication, however, the characteristics of human body channels differ according to surrounding environments, which may generate noise at a particular frequency band. In addition, interference that may be caused as users who are in human-body communications become close to each other, as well as heavy interference induced from an electronic device is problematic. Thus, in terms of the characteristics of human-body communications performed during the activities of daily life, rather than under particular conditions, those problems must be solved in order to ensure smooth and stable communication.